Abstract: :
Purpose: The visual acuities of mice have been determined psychophysicallyand with pattern VEPs to be about 0.6 cpd. However, these techniquesare time consuming to obtain acuity estimates. sVEPs are a moreefficient method to determine visual acuity but they have notbeen recorded in mice. The purpose of this study was to determineif sVEPs can be measured in mice to determine acuity. Methods:Five mice (C57Bl/6J) were used in this experiment. Anesthesiawas produced with a mixture of ketamine and xylazine (15 ug/gbody weight:7 ug/g body weight) injected IP. The active electrodewas a stainless steel bolt implanted 3 mm lateral to the lambda.The tip of the bolt rested on the dura. The reference electrodewas a gold wire placed against the roof of the mouth and theground was a needle under the skin near the tail. The mousewas placed in a stereotaxic (Stoelting, USA) apparatus thatheld the snout. Stimulus production and data collection werecarried out with the Enfant (Neuroscientific Corp) system. Thestimulus was a horizontally oriented sine wave grating. Thesweep consisted of eleven spatial frequencies (0.10, 0.12, 0.16,0.20, 0.25, 0.32, 0.40, 0.50, 0.63, 0.80, and 0.98 cpd). Thestimulus contrast was 80% and the temporal reversal rate (squarewave) was 4 Hz. The screen luminance was 100 cd/m2 and the screensubtended 100 (H) by 82 (V) at the mouse eye. Each spatial frequencywas presented for 1 second so that the entire sweep took 12seconds (11 spatial frequencies + 1 second pre-adaptation).Sweeps were averaged until the error bars for the data werestable. Results: The amplitude of the response (i.e., the secondharmonic of the discrete Fourier transform) was plotted againstspatial frequency. Acuity was determined by: 1. extrapolatingthe high spatial frequency data to the X-axis (N = 2) or 2.taking the highest spatial frequency above noise that produceda reliable response (N = 3). The average acuity for the micewas 0.76 +/- 0.079 cpd (mean +/- SD). This corresponds to anacuity of 20/789 and agrees with previous acuity estimates formice. Conclusion: sVEPs are a fast, reliable means of obtainingvisual acuity in mice.